Effects Of Environmental Factors On Anaerobic Granular Sludge In Upflow Anaerobic Sludge Blanket Reactors

Effects of environmental factors (micronutrients and toxicants) on high rate anaerobic digestion and anaerobic granular sludge were studied in laboratory-scale (20 litres) and bench-scale (1.2 litres) upflow anaerobic sludge blanket (UASB) reactors.;The anaerobic bacteria, when grown in feed lacking iron and cobalt, could become iron and/or cobalt deficient and had low specific activity. Supplements of iron and cobalt in the feed provided sufficient amount of these elements for the bacterial metabolism, and excellent COD digestion rates could be maintained in the reactors. Yeast extract showed a strong positive effect on the bacterial growth rate, but had no significant contribution to the specific activity of bacteria.;The bacterial growth rate was enhanced by high COD loading rates, and by supplements of yeast extract and vitamins. High concentrations of sulfite in the feed also favoured bacterial growth rate. High bacterial growth rates in the reactors increased organic matter inside the granules and negatively affected the granule settling properties. By contrast, inorganic cations in the feed, especially calcium, tended to form inorganic precipitates in the granules and therefore promoted the granule settling rate. The extractable extracellular polymeric substance (EPS), excreted by the anaerobic bacteria, was affected by the environmental factors. The carbohydrate concentration in the extracted EPS was significantly related to the supplements of iron and yeast extract in the feed.;Minimal sulfite toxicity was observed under gradual and shock load conditions at sulfite concentrations of up to 1000 mg S/l if proper process acclimation was allowed to occur. No inhibition was caused by the generated sulfide in the effluent when its concentration was 310 mg/l. The COD digestion rate was inhibited at a cadmium dosage of 2.0 g/l under both acclimation and shock load conditions. Most added cadmium was removed in the inorganic precipitate or absorbed by granular sludge. The bacteria could not be reactivated after being poisoned by cadmium.;A heterogenous microbial population, including Methanothrix-like, Methanobrevibacter-like, Methanococcales-like, Pelobacter-like and Spirochaete, was present on the granule surfaces. Methanothrix-like bacteria dominated in the inner-layer of all granules. Supplements of trace metals, yeast extract and sulfite did not significantly change the bacterial population

Discretionary Loan Loss Provisions And Earnings Management For The Banking Industry

The purpose of the study is to investigate the relation between discretionary loan loss provisions and 6 indicators of bank operating performance for the period 1999-2004 under controlling the type of bank, ownership status and asset size. Besides, we investigate whether bank managers intend to use discretionary loan loss provisions as a means for earnings management. Based on the empirical results from the Taiwan Economic Journal (TEJ) database, the study finds: (1) the two earnings-related variables, namely earnings before loan loss provisions and one-year-ahead earnings, are significantly related to discretionary loan loss provision; (2) non-performing loans is significantly related to discretionary loan loss provisions, but non-performing loans ratio and bad debts coverage ratio are not found to be significantly linked to discretionary loan loss provisions; (3) capital adequacy ratio is not significantly related to discretionary loan loss provisions. Finally, our findings indicate that bank managers may use discretionary loan loss provisions to engage in earnings management when the earnings before loan loss provisions or non-performing loans are at a high level

Tunable Goos-H\"{a}nchen shift and polarization beam splitter in electro-optic crystals

We have investigated the tunable lateral shift and polarization beam splitting of the transmitted light beam through electro-optic crystals, based on the Pockels effect. The positive and negative lateral shifts could be easily controlled by adjusting the permittivity tensor, which is modulated by the external applied electric field. An alternative way to realize the polarization beam splitter was also proposed by the polarization-dependent lateral shifts. Numerical simulations for Gaussian-shaped incident beam have demonstrated the above theoretical results obtained by stationary phase method. All these phenomena have potential applications in optical devices.Comment: 5 pages, 7 figure

PROCESS SCALE-UP AND OPTIMIZATION FOR PRODUCTION OF HIGH EFFICACY ORAL RABIES VACCINE

Rabies is an important causative agent of disease resulting in an acute infection of the nervous system and death of the individual. Rabies remains an important public health program in developing countries, and the indigenous threat of rabies continues in developed countries because of wildlife reservoirs. Globally, there are about 55,000 fatal human cases of rabies each year [WHO, 2007]. Control of rabies in wildlife remains an important challenge for government offices. There are numbers of rabies vaccines commercially available for controls of wildlife rabies. However, these vaccines currently distributed to wildlife do not effectively immunize all at-risk species, especially skunks. Alternative efficacious vaccines are needed. A human adenovirus rabies glycoprotein recombinant vaccine candidate (AdRG1.3), developed by the Rabies Research and Development Unit at Ontario Ministry of Natural Resources, Canada, has shown the most promising result in laboratory trials. The adenovirus used in rabies vaccine laden bait is produced using HEK 293 cell culture process. This presentation will focus on demonstrating the successful scale-up of AdRG1.3 adenovirus production from 1 liter to 500 liter to manufacture large quantities of bulk material required to support field trials and demonstrate efficacy of this new vaccine. The robustness of production process was improved through elimination of medium replacement operation at the time of virus infection, and culture titer was increased by over 3 folds through optimization of cell culture medium. The elimination of medium replacement step reduced the risk of culture contamination, and resulted in significant saving in material expenses and reduction in labor costs. Over 10,000 liters of active AdRG1.3 adenovirus cultures were manufactured so far to support field trials. AdRG1.3 adenovirus is formulated and packaged in baits using Artemis Technologies Inc. proprietary technology prior to aerial-baiting. AdRG1.3 rabies vaccine has been distributed by several provincial agencies to testing areas located in Ontario, Quebec and New Brunswick provinces, Canada, for field trials in yearly campaigns from 2006 to 2009. The field results showed that the new vaccine was more efficient than the existing ones in immunizing animals that were previously difficult to vaccinate

Suspension Vero cell culture technology for high titer production of viral vaccines

Vero cells are considered as the most widely accepted continuous cell line by the regulatory authorities (such as WHO) for the manufacture of viral vaccines for human use. The continuous Vero cell line has been commercially used, after propagation on microcarriers, for the production of rabies, polio, enterovirus 71, hantaan, more recent COVID19 and other vaccines. Vero cell culture technologies were also explored for productions of many more viral vaccines over the last two decades. The growth of Vero cells is anchorage-dependent, and cells need to be dissociated enzymatically or mechanically for the process of subcultivation. This process is labor intensive and complicated in process scale-up. Adaptation of Vero cells to grow in suspension will significantly simplify scale-up and manufacturing processes. Development of advanced suspension Vero culture technology to improve product titer will further reduce the cost of goods. We previously reported a successful adaptation of adherent Vero cells originated from ATCC CCL-81 to grow in suspension in serum-free and animal component-free media developed in-house. The suspension adapted cells were found to retain their genetic stability and to be non-tumorigenic. Present work continues the development and optimization of cell culture process and feeding strategy to improve the growth of suspension Vero cell and the production of vesicular stomatitis virus (VSV) and herpes simplex virus-1 (HSV-1). Data from this study showed the suspension adapted Vero cells retained similar VSV productivity to that obtained in adherent culture; volumetric productivity of VSV increased with the increasing cell density at infection in batch culture. However, the maximum cell density in batch culture was about 2.5x106 cells/mL, and was not improved significantly despite tremendous effort dedicated to improve culture conditions such as supplementing various nutrients in batch culture. As a result, perfusion culture was employed as an approach to increase cell density in the culture, which in turn increased the VSV productivity up to one log, at 1.1x1010 TCID50/mL when the culture infected at 7x106 cells/mL. High titer production of HSV-1 in the Vero culture is more challenging. The virus productivity is not only limited by the maximum cell density in batch culture, but also reduced by inhibitory metabolites secreted in the culture even at low cell density such as 1x106 cells/mL. Media replacement before virus infection is essential to achieve a high HSV-1 yield. As such, perfusion culture was a preferred mode for high titer production of HSV-1, which improved the HSV-1 titer also by up to one log to 1.8 x109 TCID50/ in a culture infected at 5x106 cells/mL when comparing to a control shake flask culture infected at 1x106 cells/mL. Experimental data also demonstrated that perfusion Vero culture was robust and reproducible. This study demonstrates that batch or perfusion suspension Vero culture is a much simplified process than current adherent culture technology for manufacturing of viral vaccines, and offers great potentials in reducing the cost of goods. The suspension Vero culture developed in our institute has generated tremendous interests from industry and academia, and are being tested by many different organizations

Development of suspension adapted Vero cell culture process technology for production of viral vaccines

Abstract Vero cells are considered as the most widely accepted continuous cell line by the regulatory authorities (such as WHO) for the manufacture of viral vaccines for human use. The growth of Vero cells is anchorage-dependent. Scale-up and manufacturing in adherent cultures are labor intensive and complicated. Adaptation of Vero cells to grow in suspension will simplify subcultivation and process scale-up significantly, and therefore reduce the production cost. Here we report on a successful adaptation of adherent Vero cells to grow in suspension in a serum-free and animal component-free medium (IHM03) developed in-house. The suspension adapted Vero cell cultures in IHM03 grew to similar or better maximum cell density as what was observed for the adherent Vero cells grown in commercial serum-free media and with a cell doubling time of 40–44 h. Much higher cell density (8 × 10 6 cells/mL) was achieved in a batch culture when three volume of the culture medium was replaced during the batch culture process. Both adherent and suspension Vero cells from various stages were tested for their authenticity using short tandem repeat analysis. Testing result indicates that all Vero cell samples had 100% concordance with the Vero DNA control sample, indicating the suspension cells maintained their genetic stability. Furthermore, suspension Vero cells at a passage number of 163 were assayed for tumorigenicity, and were not found to be tumorigenic. The viral productivity of suspension Vero cells was evaluated by using vesicular stomatitis virus (VSV) as a model. The suspension cell culture showed a better productivity of VSV than the adherent Vero cell culture. In addition, the suspension culture could be infected at higher cell densities, thus improving the volumetric virus productivity. More than one log of increase in the VSV productivity was achieved in a 3L bioreactor perfusion culture infected at a cell density of 6.8 × 10 6 cells/mL

Development of suspensions adapted Vero cell culture process for production of viruses

Vero cells are considered as the most widely accepted continuous cell line by the regulatory authorities (such as WHO) for the manufacture of viral vaccines for human use. The continuous Vero cell line has been commercially used, after propagation on microcarriers, for the production of rabies, polio, enterovirus 71 and hantaan virus vaccines. Vero cell culture technologies are also explored for productions of many more viral vaccines over the last two decades. The growth of Vero cells is anchorage-dependent, and cells need to be dissociated enzymatically or mechanically for the process of subcultivation. This process is labor intensive and complicated in process scale-up. Adaptation of Vero cells to grow in suspension will simplify subcultivation and process scale-up significantly. Here we report on the adaptation of adherent Vero cells to grow in suspension using a serum-free and animal component-free medium developed in-house. The maximum cell density and cell doubling time of the suspension adapted Vero cells in batch culture grown in the in-house developed medium were similar to or better than what was observed for the adherent Vero cells grown in commercial media. The growth of suspension adapted Vero culture was successfully scaled up to 3 L bioreactor. The Vero cells from various stages (both adherent and adapted) were tested for their authenticity using a Short Tandem Repeat (STR) analysis. The testing result indicates that all Vero cell samples have 100% concordance with the Vero DNA control sample, indicating the suspension adapted cells maintained their genetic stability. Productions of vesicular stomatitis virus (VSV) and influenza virus in adherent culture and suspension adapted culture were compared, showing the suspension adapted Vero cell retained similar viral productivity. The volumetric productivity of VSV in the suspension culture was even higher, and was further increased by almost 200 times when culture was infected at higher cell density and with medium replacement before the virus infection. In contrast, the VSV production decreased when the adherent culture was infected at higher cell density. Additional process development revealed that the maximum cell density in batch culture was doubled, reaching 6x106 cells/mL, when the culture medium was replaced during the process of batch culture, which indicates potential for further increases in product titer

A new polymorph of 5,5′-(ethane-1,2-di­yl)bis­(1H-tetra­zole)

The asymmetric unit of the title compound, C4H6N8, contains a quarter of the mol­ecule, which possesses a crystallographically imposed centre of symmetry with all non-H atoms situated on a mirror plane. The crystal packing exhibits inter­molecular N—H⋯N hydrogen bonds and π–π stacking inter­actions between the tetra­zole rings of adjacent mol­ecules [centroid–centroid distance = 3.4402 (10) Å]